Presenting intermixed waveform, character and graphic information on a single display of a medical monitoring system permits an observer to have essential patient information available at one place and time. Previously directed beam cathode ray tubes have typically been used as the display means for monitoring systems. Presentation of characters and graphics on a directed beam display requires complex, fast deflection circuitry and complex vector drive capability to draw the characters and graphics without losing too much display brightness.
These difficulties may be avoided by using a cathode ray tube in which the electron beam is resonantly deflected so as to scan a raster of parallel paths covering the screen. The time during which the beam is turned off for beam positioning is known and minimal so as to permit filling the display with characters in addition to graphical information without reducing the brightness of the display. When, however, a waveform is reproduced by display systems using a raster scan that forms contrast in light within spaced parallel paths in such a manner that the contrast is changed at points where the waveform intersects the paths, the waveform appears as a series of dots. It can be made to appear as a nearly continuous line if the paths are close enough together, but the expense of producing this fine a raster is prohibitive. Some improvement has been attained with an economical line spacing by elongating the dots along the paths so that one dot does not terminate until the next one begins. This results in a jagged line that may be satisfactory for many applications, but it is not satisfactory for representing certain physiological functions, such as cardiac electrical action, because the jaggedness of the line makes it difficult for the viewer to make an accurate interpretation.